Composition of matter



Patented Sept. '10, 1940 UNITED STATES COMPOSITION OF MATTER Marselio G. Fontana, Lancaster Village, Del., as-

signor to E. I. du Pont de Nemours & Company, Wilmington, Del., a. corporation of Delaware No Drawing. Application May'27, 1939, Serial No. 276,047

3 Claims.

This invention relates to alloys. More particularly, the invention relates to a corrosion-resistant alloy which is capable of fabrication. Still more particularly, the invention relates to a nickel-chromium-steel alloy that is capable of fabrication.

Nickel-chromium-steel alloys have been long lmown and widely used. The alloys of the prior art while useful for many purposes lack the necessary corrosion resistance for some purposes, and this is especially true where such resistance is necessary in a metal which must be forged, rolled and/or otherwise fabricated.

This invention has as an object a new alloy. A further object of the invention is a new alloy with increased corrosion-resistant characteristics. A still further object is a new corrosionresistant alloy capable of fabrication. Other objects will appear hereinafter.

These objects are accomplished according to the invention by'the discovery that a highly corrosion-resistant alloy capable of being fabricated can be obtained by combining nickel, chromium, molybdenum, copper, manganese, iron and carbon in definite proportions, with or without small amounts of phosphorus and sulfur and with the normal amount of silicon which is usually unavoidably present in such alloys.

In order that the invention may be more thoroughly understood, the following example is given showing the proportions of the constituents, but it is to be understood that the invention is not restricted thereto but is capable of variation within limits hereinafter set forth.

EXAMPLE Per cent Nickel 27.0 Chromium 20.0 Molybdenum 3.5 Copper 2.0 Silicon L 1.0 Manganese 2.0 Carbon 0.08 Iron 44.42

While the above example discloses one embodiment of the invention, the operative limits are as follows:

Per cent Nickel; 24 to 40 5 Chromium 15 to 25 Molybdenum 2 to 6 Copper 1 to 4 Silicon 0.5 to 2 Manganese 1.0to 4 10 Carbon Up to 0.12 Sulfur Up to 0.02 Phosphorus Up to 0.02 And the remainder iron. 15

Within the limits as set forth above, it has been found that the following proportions are especially suitable to accomplish the objects of the invention, and hereby, they consist of the preferred embodiment of the invention. 20

Per cent Nickel 26 to 28 Chromium 19 to 21 Molybdenum 3.25 to 3.75 n Copper 1.8 to 2.2 Silicon 0.8 to 1.2 Manganese 1.8 to 2.2 Carbon Up to 0.12 Sulfur Up to 0.02 Phosphorus Up to 0.02 30 And the remainder iron.

It will be readily apparent that this alloy is a variation of the well-known nickel-chromiummolybdenum-steel combination, and advantage 35 is taken of the corrosion-resistant characteristics of the nickel, chromium, and molybdenum. These constituents alone, however, are not capable of producing a highly corrosion-resistant alloy which can be easily fabricated. 40

Copper is added to further control the corrosion-resistant characteristics. When used in the proportions as above set forth and in combination with the other constituents, the copper brings the alloys to a point where it is highly 45 resistant to extremely corrosive materials, such, for example, as sulphuric acid and nitric acid.

Manganese, when used in the proportions as set forth above, adds to the new alloy the quality of ease of fabrication. Thus, for example, the new alloy can be readily forged into bars and rolled into sheets. Bars and sheets formed from the new alloy are substantially free from checks and cracks. Furthermore, manganese when used in the proportions herein set forth does not detract from the corrosion resistance of the alloy. Sulfur and phosphorus are impurities in the iron and their proportions should be kept within I the limits as set forth above.

The steel alloy of the present invention is further characterized in that its carbon content should be kept low, and this is especially true when the alloy is to come in contact with nitric acid.

Iron is to constitute the remainder of the alloy, said constituent always being present in amounts of 35% or greater.

In order to illustrate the extremely high corrosion-resistant characteristics of this alloy to sulfuric acid atvarious concentrations, the following table is presented.

Table I Conccntra- Inches Corrosion agent tion in per penetration cent per month Sulphuric acid 10 0.00003 The alloy upon which the above tests were made had the following proportions:

. alloys are extremely resistant to sulfuric acids of all strengths.

One of the most surprising qualities of this new alloy is its high strength when compared with prior alloys of this general type. Tests conducted on one set of standard test specimens in the as forged condition gave the following results:

Ultimate strength lbs./sq. in. 112,000 Yield point (0.0002 inch permanent deformation on a 2 inch gage length) lbs/sq. in. 73,500 Elongation in 2 inches Per cent..- 31.5 Reduction of area do 58.0 Brinell hardness 223 Impact strength (Izod) 79 This new alloy has found many uses, particularly in the chemical industry. Several of these uses will, by way of illustration only, be set forth, but it is to be understood that the alloys of the present invention are not to be limited in scope thereto. Due to its highly corrosion-resistant characteristic to sulfuric acid, the new alloy can be advantageously used in all processes involving sulfates and sulfuric acid. Apparatus for the above mentioned processes in which the new alloy may be used consists of condensers, valves, burners, reaction chambers, tanks, etc.

7 Because of its high stress properties and the ease with which the metal may be machined and fabricated, the new alloy lends itself readily to the manufacture of nuts, bolts, flanges, studs, strips, plates, and the like.

In the invention, no claim is made to the mere combining of the above constituents in an alloy, but what I do claim is the particular alloy having the proportions set forth in the claims.

I claim:

1. A high tensile strength corrosion-resistant alloy of good forgeability and machineability, comprising 27% nickel, 20% chromium, 3.5% molybdenum, 2% copper, 1% silicon, 2% manganese, 0.08% carbon and the balance substantially all iron.

2. A high tensile strength corrosion-resistant alloy of good forgeability and machineability, containing 26-28% nickel, 19-21% chromium, 3.25-3.75% molybdenum, 1.8-2.2% copper, 08-12% silicon, 1.8-2.2% manganese, up to 0.12% carbon, up to 0.02% phosphorus, up to 0.02% sulfur and the remainder substantially all iron.

3. An alloy of the class described and containing 25-35% nickel, 15-23% chromium, 2-5% molybdenum, 1 .5-3% copper, 0.75-1.5% silicon, 1 -4% manganese, up to 0.12% carbon, up to 0.02% sulfur, up to 0.02% phosphorus and the balance substantially all iron.

MARSELIO G. FONTANA. 

